Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 65: Poster: Molecular Nanostructures on Surfaces

O 65.6: Poster

Mittwoch, 20. März 2024, 18:00–20:00, Poster C

Photoinduced increase of the local molecular coverage on a surface — •Christophe Nacci and Leonhard Grill — Institute of Chemistry, University of Graz, Graz, Austria

Ullmann coupling is one of the preferred reactions to synthesize covalent molecular architectures on surfaces [1]. The dissociation of specific substituents carried by the molecular precursors as well as the formation of new bonds can be triggered by different external stimuli, for instance heat, light and electric current. While the thermal control of on-surface chemical reactions is a well-established approach, only few studies report the on-surface polymerization by light.

Here, light-induced chemical reactions of an anthracene derivative on a surface [2] were investigated by combining low-temperature scanning tunneling microscopy and X-ray photoemission spectroscopy. Special emphasis is on the spatial distribution of the products, studied by position-dependent measurements. Polymerization takes place only in a limited portion of the surface, i.e., at the areas hit by the most intense laser spot. A significant increase of the local molecular coverage is observed and mainly ascribed to the local interplay between thermally induced diffusion of the adsorbed species and the reduced mobility of the grown oligomers. Moreover, despite long UV irradiations, debromination of the adsorbed species never progresses to completion within the experiment time.

[1] L. Grill and S. Hecht, Nature Chem. 12, 115 (2020) [2] C. Nacci et al., J. Phys. Chem. C 125, 22554 (2021)

Keywords: On-surface synthesis; Scanning tunneling microscopy; Ligh-induced reactions; Photopolymerization; Polymers